By studying the thermal conductivity,specific heat,elastic modulus,and thermal expansion as a function of temperature for Cd_(3)As_(2),we have unveiled a couple of important thermodynamic features of the low-energy ph...By studying the thermal conductivity,specific heat,elastic modulus,and thermal expansion as a function of temperature for Cd_(3)As_(2),we have unveiled a couple of important thermodynamic features of the low-energy phonons strongly interacting with Dirac electrons.The existence of soft optical phonons,as inferred from the extremely low thermal conductivity,is unambiguously confirmed by low-temperature specific heat revealing significant deviation from Debye's description.The estimated Debye temperature is small in the range of 100-200 K and varies significantly depending upon the measurement used in its experimental determination.The thermodynamic Gr¨uneisen ratioγreveals a remarkable reduction below about 100 K,an energy scale that is highly relevant to the Dirac states,towards negative values below about 10 K that are indicative of lattice instability.展开更多
Mn_(3)Sn_(2)has been proposed as an ideal material for magnetic refrigeration.It undergoes two successive ferromagnetic transitions(T_(C1)=262 K and T_(C2)=227 K)and one antiferromagnetic transition(TN=192 K).Herein w...Mn_(3)Sn_(2)has been proposed as an ideal material for magnetic refrigeration.It undergoes two successive ferromagnetic transitions(T_(C1)=262 K and T_(C2)=227 K)and one antiferromagnetic transition(TN=192 K).Herein we report,for the first time,the preparation of single crystals of Mn_(3)Sn_(2)from Bi flux.The resultant anisotropic magnetic properties and magnetocaloric effect are investigated along the three principal crystallographic directions of the crystal.Significant anisotropy of magnetic susceptibility and multiple field-induced metamagnetic transitions were found at low fields,whereas the magnetocaloric effect was found to be almost isotropic and larger than that of the polycrystalline one.The maximum magnetic entropy change amounts to-ΔSM=4.01 J·kg^(-1)·K^(-1)near T_(C1)under a magnetic field change of μ_(0)ΔH=5 T along the c-axis,with the corresponding refrigerant capacity of 1750 mJ·cm^(-3).Combined with a much wider cooling temperature span(~80 K),our results demonstrate Mn_(3)Sn_(2)single crystal to be an attractive candidate working material for active magnetic refrigeration at low temperatures.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11974389,12141002 and 52088101)the National Key R&D Program of China(Grant No.2017YFA0303100)+1 种基金the Chinese Academy of Sciences through the Scientific Instrument Developing Project(Grant No.ZDKYYQ20210003)the Strategic Priority Research Program(Grant No.XDB33000000)。
文摘By studying the thermal conductivity,specific heat,elastic modulus,and thermal expansion as a function of temperature for Cd_(3)As_(2),we have unveiled a couple of important thermodynamic features of the low-energy phonons strongly interacting with Dirac electrons.The existence of soft optical phonons,as inferred from the extremely low thermal conductivity,is unambiguously confirmed by low-temperature specific heat revealing significant deviation from Debye's description.The estimated Debye temperature is small in the range of 100-200 K and varies significantly depending upon the measurement used in its experimental determination.The thermodynamic Gr¨uneisen ratioγreveals a remarkable reduction below about 100 K,an energy scale that is highly relevant to the Dirac states,towards negative values below about 10 K that are indicative of lattice instability.
基金supported by the National Natural Science Foundation of China(Grant No.12274440)the Strategic Priority Research Program(B)of Chinese Academy of Sciences(Grant No.XDB33010100)National Key R&D Program of China(Grant No.2022YFA1403903)。
文摘Mn_(3)Sn_(2)has been proposed as an ideal material for magnetic refrigeration.It undergoes two successive ferromagnetic transitions(T_(C1)=262 K and T_(C2)=227 K)and one antiferromagnetic transition(TN=192 K).Herein we report,for the first time,the preparation of single crystals of Mn_(3)Sn_(2)from Bi flux.The resultant anisotropic magnetic properties and magnetocaloric effect are investigated along the three principal crystallographic directions of the crystal.Significant anisotropy of magnetic susceptibility and multiple field-induced metamagnetic transitions were found at low fields,whereas the magnetocaloric effect was found to be almost isotropic and larger than that of the polycrystalline one.The maximum magnetic entropy change amounts to-ΔSM=4.01 J·kg^(-1)·K^(-1)near T_(C1)under a magnetic field change of μ_(0)ΔH=5 T along the c-axis,with the corresponding refrigerant capacity of 1750 mJ·cm^(-3).Combined with a much wider cooling temperature span(~80 K),our results demonstrate Mn_(3)Sn_(2)single crystal to be an attractive candidate working material for active magnetic refrigeration at low temperatures.
基金supported by the National Natural Science Foundation of China (12141002,52088101,11874417,11974389,and 52172216)the Ministry of Science and Technology of China (2021YFA0718702)+5 种基金the Chinese Academy of Sciences through the Strategic Priority Research Programthe Scientific Instrument Developing Programthe Project for Young Scientists in Basic Research (XDB33000000,YJKYYQ20200017,and YSBR-057)the Chinese Postdoctoral Science Foundation (E0BK181)the funding support of the National Key Research and Development Program of China (2018YFA0702100)the support from the Key Research Project of Zhejiang Laboratory (2021PE0AC02)。
